This invention relates to a new and useful improvement in the mechanical joint for pipe, particularly when conforming to the standardized dimensions in ANSI/AWWA C111/A21.11, American National Standard for Rubber-Gasketed Joints for Ductile-Iron and Gray-Iron Pipe and Fittings, and used on pipeline appurtenances such as gate valves and fittings.
The joint in question and improvements thereto has been the subject of many U.S. patents, among them: U.S. Pat. Nos. 1,365,530; 1,556,745; 1,873,620; 1,873,621; 1,960,750; 2,282,738 and others. The joint has received wide acceptance and now has its dimensions standardized. This invention involves improvements to the standardized mechanical joint mentioned above. Throughout this patent the words "standardized mechanical joint, standardized T-bolt, or standardized nut" will refer to the standardized dimensions, description, and method of assembly shown in the abovementioned standard and its appendices. Use of the standardized mechanical joint and some alternate dimensions are also found in the following standards: ANSI/AWWA C110/A21.10 American National Standard for Gray-Iron and Ductile-Iron Fittings, 3 In. through 48 In. for Water or Other Liquids; ANSI/AWWA C153/A21.53, American National Standard for Ductile-Iron Compact Fittings, 3 In. through 12 In. for Water or Other Liquids; AWWA C500, AWWA Standard for Gate valves 3 In. through 48 In. for Water and Other Liquids; AWWA C509,AWWA Standard for Resilient Seated Gate Valves 3 In. through 12 In. for Water or Other Liquids. With some few exceptions, the same dimensions are listed or refered to in all these standards. The word "standardized" used in conjunction with an item is not to exclude the use of that item found in any of the abovementioned standards or any use wherein ANSI/AWWA C111/A21.11 is referenced.
The standardized mechanical joint has been included in the waterworks specification of the majority of cities and towns in the United States. Although the joint was designed for pipe and fittings it has become the most widely used joint on waterworks valves. The problem which this invention addresses arises for the most part from the prior art use of the standardized mechanical joint on gate valves. In the size range 3" through 12" gate valves require one or more slots instead of bolt holes due to the inability to insert the required standardized T-bolt. This is caused by the valve body casting surface being too close to the standardized bell flange.
Therefore, it is the object of this invention to provide an improved means of assembly of the standardized mechanical joint on pipeline appurtenances having shape or dimensions which prevent the insertion of the standardized T-bolt, particularly on gate valves and compact fittings as found in ANSI/AWWA C153/A21.53.
The ordinary prior art method of assembly is to:
a. Place the gland on the pipe or fitting spigot. PA1 b. Place the gasket on said spigot in front of gland. PA1 c. Insert said spigot into the standardized mechanical joint socket. PA1 d. Push said gland and gasket forward. PA1 e. Align the gland bolt holes with the bell flange bolt holes and extend the T-bolts through the bell flange and gland bolt holes in that order. PA1 f. Connect the standardized nut to the threaded end of the T-bolt. PA1 g. Tighten each nut to the torque required to prevent leakage. PA1 a. The gland, gasket, socket, and spigot are positioned and aligned as described in the prior art. PA1 b. Standardized T-bolts are inserted, if possible, from the valve side of the joint, extending through bell flange and gland bolt holes respectively. PA1 c. In all cases where the standardized T-bolts cannot be inserted as described, the said special screws are inserted from the gland side, through the gland bolt hole and bell flange bolt hole respectively. PA1 d. The screw is threadably ingaged to the nut means. PA1 e. All standardized nuts and special screw heads are torqued to the level of torque so as to prevent leakage. This torquing operation can be accomplished by using one hand only, as is often necessary.
The standardized nut is a heavy hex nut. Because of the added height of the heavy hex nut, a ratchet type socket wrench is very stable during tightening and the standardized nuts can be torqued with one hand.
In the case of assembly of the standardized mechanical joint when said joint is a part of a gate valve conforming to AWWA C500, standardized T-bolts are inserted as described above except for the two bolts closest to the vertical centerline of the valve. Because of the close fit, the two bolt holes closest to the vertical centerline are replaced with slots. The standardized T-bolt is placed in the slot and tightened by torquing the nut. In most cases the standardized T-bolt will not stay in place while tightening. Valves are therefore provided with special T-bolts having a side lug to prevent the bolt from turning during tightening. It often occurs that during tightening the thin section of valve body below the slot will fail by cracking. This is catastrophic since leakage occurs and usually the entire valve is replaced.